Protective device for electric circuits.



L. E. DICKINSON." PROTECTIVE DEVICE FOR ELECTRIC CIRCUITS. APPLICATIONTILED NOV- 6.1916.

1,252,412. Patented Jan. 1918.

TUNITEWD STATES PATENT OFFICE.

LEWIS E. DICKINSON, OF BOONTON, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRICCOMPANY, INCORPORATED, 011' NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PROTECTIVE DEVICE FOR ELECTRIC CIRCUITS.

Patented Jan. 8, 1918. 4 Application filed November 6, 1916. Serial No,129,767.

1,252,412 Specification of Letters Patent.

To all whom it may concern:

Be it known that I, Lnwrs EDMUND DICK- INsoN, a citizen of the UnitedStates, residing at Boonton, in the county of Morris generated by thecurrent flowing tl'irough the heating element is concentrated at a givenpoint and very efliciently utilized in melting the fusible material, thesoftel'iing and State of New Jersey, have invented of whichallows thedevice to function and certain new and useful Improvements in protectthe apparatus. This is accomplished Protective Devices for ElectricCircuits, by making the metal parts which are joined of which, thefollowing is a full, clear, conby the fusible metal small in mass, andheatcise, and exact description. insulating these parts from thesurround- This invention relates to protective deing metal parts of theprotective device and vices for electric circuits, and more particitsmountings. ularly to heat coils for the protection of The severalfeatures of this invention telephone apparatus against abnormal curmaybe more readily understood by referrents, which, although not ofsuflicient value ence to the accompanying drawing in which to operatethe fuses, would, if allowed to there is shown a cross-sectional view ofa flow, result in injury to the apparatus. preferred type of heat coil,wherein. 1 repn the type of heat coils commonly used, resents a pin ofwood or other suitable heat it is the general practice to employ a metalinsulating material having a recessed porpin as a switching member, thispin being tion in which a strip of metal foil 2 is fastened to a metalsleeve by means of low wrapped and priclcpunched to hold it in fusingsolder, which is. softened through place. Surrounding this portion ofthe pin the medium of heat generated by abnormal is a thin metal tube orsleeve 3, preferably currents which flow through the heating of copper,one end of which is flared out or element. In still other types, partsof the flanged, as shown at 4, and a washer 5 of heat coils are soldereddirectly to the mountfiber or other non-heat-conducting material ingsprings. However, in all of these types is placed over this tube andagainst the the parts joined by, the low fusing solder fiared-outportion. A second washer 6 of are of relatively generoussize, therebyrefiber or other non heateonducting mate quiring that a considerableamount of heat rial is, placed against the flared-out end of begenerated before these parts are raised the tube, and a metal band 7 isspun .over

to the temperature at which the solder be comes plastic. Not only isconsiderable heat taken up by these parts, due to their mass, but noprovision is made for the heat insulation of these parts from thesurrounding metal parts of the device itself or the mounting springswhich act as additional conducting and radiating surfaces. It thereforebecomes necessary to generate an amount of heat far in excess of thatutilized for melting the solder, which in turn necessitates a' heatingelement of high resistance. The object of this invention is to provide aheat coil which will not'only be certain and reliable in its operation,but which will also be very efficient in o 'ieralion, thereby making itpossible to decrease the resistance of the heating element. Since thisheating element is placed directly in the line circuit, it highlyimportant that its resistance be kept as low as possible, especially inthe case of heat coils to be used on long and expensive toll lines.

To attain these objects thisinvcntion consists of improvements wherebythe heat the washers to make them a unitary strucover the pin 1, and adrop of low melting solder 9 is inserted in the perforation 10 of thetube, which, when solidified, holds the pin and tube rigidly together.IA winding 11, preferably of a material having a high positivetemperature coeflicient, is placed over the tube 3, one end being'firstconnected tothe metal band 7. The assembled pin and tube are then placedwithin the shell 12. which is of bakelite or other insulating material,and into one end of which is crimped a metal cap 13. The end of the pinextends into the hollow hub 14 of the metal cap 13, and is rigidlyfastened by means of a crimping or staking operation. The assembly ofthe heat .coil is then completed by drawing the unfastencd end of thewinding through a slot in the shell and soldering it to the cap 13.

As the method of inserting coils of the i of August 17, 1897, it isthought to be unnecessary to illustrate the method in the present case.

In service the heat coil is under spring pressure, and in case thesolder is softened;

by abnormal currents in winding 11, relative movement is permittedbetween the pin 1 and the sleeve 3, allowing said pin to project fartherthrough the sleeve, and in so doing, to ground the line in thewell-known manner as illustrated by the patent herein before referredto. While the device shown is a preferred type, there are manymodifications which might be made without in any way departing from thespirit of the invention. For example, under certain conditions, it mightbe preferable to employ a metal pin instead of one ofwood or othersimilar material. Such a construction would be slightly less efficientthan that shown, since it would increase the massof-metal in the. deviceto be heated, but the construction nevertheless, would be such as toprevent any considerable amount of heat being con-. ducted away to themounting springs. Again, where a pin of insulating material is used,instead of Wrapping a piece of metal foil in the recessed portion of thepin, it

might be found preferable to. resort to the use of a metal ring moldedon the pin.

What is claimed is: 1. In a protective device for telephone cuits, asleeve of heat-conducti1ig material,

a circuit controlling element extending through said sleeve,heat-softena'ble material for mechanically oining saidsleeve and saidCIIOUItOOIItI'OIllIlg element, a heatgenerating element, terminals forsaid heatgeneratmg element, and means for normally insulating saidsleeve from said terminals.

2. Irra protective device fortelephone cir- .cults, a sleeve of.heat-conductin material,

a cireuit-controlling element 0 non-conducting material extendingthrough said sleeve, heat-softenable material for mechanically joiningsaid sleeve and said circuit-controlling element, a heat-generatingelement, terminals Qfor said heatgenerating element, and meansfornormally insulating said sleeve from said terminals.

3. In a protective device for telephone circuits, a sleeve ofheat-conducting material,

a circilit-controllingelement of non-conduct ing material extendingthrough said'sleeve and provided with a metallic section for attachmentto said sleeve, and heat-softenable material for mechanically joiningsaid sleeve and said circuit-controlling element.

4. In a protective device for telephone tachment to said sleeve,heat-softenable mamgsaid s eeve from said terminals.

for attachment to said sleeve, heat-softe'nable material for mechanicalljoining said sleeve and said circuit-control ing element, aheat-generating element, terminals for said heat-generatin element, andmeans for insulating said 5 eeve from said terminals. v

5. In a protective device for telephone cirouits, a sleeve ofheat-conducting material. a circuit-controlling element ofnon-conducting-material extending through said sleeve and provided witha metallic section for atterial for mechanically joining said sleeve andsaid circuitcontrolling element, aheatgenerating element composed ofmaterial having a high positive temperature coefficient, terminals forsaid heat-generating' ee element, and means for insulating said sleevefrom said terminals.

6. In a protective device for telephone circuits, a shell ofnon-conducting material, a metal cap attached to one end of said shell,said cap being provided with a hollow hub into which extends acircuit-controlling element, a sleeve of heat-conducting materialsurrounding a portion of said circuit-controlling' element, heatsoftenable material for mechanically joining said sleeve and saidcircuit controlling element, a heat gen erating element, terminals forsaid heat generatin element, and means for insulat- 7. In a rotectivedevice for telephone circuits, a sell of non-conducting material,

a metal cap attached to one end of' said shell, said cap being providedwith a hollow." Hub, and a circuit-controlling element ex tending intosaid hub.

8. In a protective device for telephone circuits, a shell ofnon-conducting material, a metal cap attached to one end of said shell,said cap being provided with a hollow hub, and a circuit-controllinelement of non-conducting material exten ing into saidihub;

9. In a protective device for telephone circuits, a sleeve ofheat-conducting material having an outward extendin member 0 one end, aterminal band earrie by said sl eve, I and insulating means between saidband nd said sleeve.

In witness whereof I hereunto subscri e my name this4th day of NovemberA. 1916..

s LEWIS E. DICKINSON.

